Cassini detects Interstellar Dust Grains at Saturn

April 15, 2016; Srama, Ralf

An article by Altobelli et al. appeared in the journal Science reporting about the
identification of interstellar dust at Saturn. Interstellar dust (ISD) is the condensed phase
of the interstellar medium. In situ data from the Cosmic Dust Analyzer on board the Cassini
spacecraft reveal that the Saturnian system is passed by ISD grains from our immediate interstellar
neighborhood, the local interstellar cloud. The mass distribution of 36 interstellar grains was
determined, their elemental composition, and a lower limit for the ISD flux at Saturn. Mass spectra
and grain dynamics suggest the presence of magnesium-rich grains of silicate and oxide composition,
partly with iron inclusions. Major rock-forming elements (magnesium, silicon, iron, and calcium)
are present in cosmic abundances, with only small grain-to-grain variations, but sulfur and carbon
are depleted. The ISD grains in the solar neighborhood appear to be homogenized, likely by repeated
processing in the interstellar medium.

The Cassini-Huygens mission is a cooperative project of NASA, ESA and the Italian Space Agency.
JPL manages the mission for NASA's Science Mission Directorate in Washington. The Cosmic Dust
Analyzer (CDA) was developed by the Max Planck Institute for Nuclear Physics (Heidelberg) and the
German Space Agency (DLR, Berlin). It is operated by the Institute for Space Systems (IRS) at
the University of Stuttgart (Principal Investigator R. Srama). The project is supported by the
German Space Administration DLR.